BERLIN (AP) — The United Nations' refugee agency urged Kenya on Tuesday to reconsider its demand for the closure of a vast camp for Somali refugees within three months.

Kenyan Deputy President William Ruto made the demand Saturday, urging the agency to send the more than 400,000 refugees living at the Dadaab camp back home or see Kenya relocate them itself. The government says Dadaab has become a recruitment center for the extremist group al-Shabab, whose gunmen killed 148 people at Kenya's Garissa College University on April 2.

The U.N. High Commissioner for Refugees is concerned that abruptly shutting Dadaab and forcing the refugees back to Somalia "would have extreme humanitarian and practical consequences, and would be a breach of Kenya's international obligations," spokeswoman Karin de Gruijl said in Geneva.

The agency is urging Nairobi to give the matter further consideration, she said, adding that it is ready to intensify work with Kenya to strengthen law enforcement at Dadaab.

She said UNHCR also is ready to work with Kenya and the Somali government to step up a pilot program launched in December to support people who want to return to three relatively safe parts of Somalia, but the agency believes that "large-scale returns are still not possible in many parts of the country."

Al-Shabab has vowed retribution on Kenya for deploying troops to Somalia in October 2011 to fight the militant group. The Garissa attack is one of the worst which extremists have carried out in the country, second only to the 1998 bombing of the U.S. embassy in Nairobi.